1. Field of the Invention
The present invention relates to a system to shape the surface of a substrate, namely, to thin and modify films, and more particularly, to a method for determining the path for a plasma assisted chemical etching material removal tool to thin and modify the thickness profile of an existing substrate layer. The present invention provides a means to obtain a layer of uniform and specified thickness from a layer having a measured, but non-uniform thickness profile.
2. Description of the Prior Art
Substrate materials with thin solid layers, such as silicon-on-insulator (SOI) wafers, and films are used extensively in the fabrication of electronic, optical, magnetic, superconducting and other important technological devices. Such substrates are often subjected to figuring and thinning processes which remove some of the material from the surface. Along with describing conventional material removal processes, a system for removing material from the surface of an SOI wafer is described in a related patent application entitled "System for Removing Material from a Wafer", U.S. patent application Ser. No. 07/696,897, filed on May 7, 1991. The system disclosed therein includes a means for determining thickness profile data for a surface of a wafer, means for converting the thickness profile data to a dwell time versus position map stored in a system controller and a means for removing material from the surface of the wafer in accordance with the map such that the wafer has a preselected thickness profile.
The present invention is directed toward a method used to determine the paths that the removal tool must make over the wafer to thin the wafer to a uniform thickness or a desired profile.